Present commercial practice is to use conventional naphthenic transformer oils in electrical devices operating under severe stress such as transformer load tap changers. Unfortunately such oils have poor oxidation and chemical stability under severe loading conditions of high current, fast contact switching speeds and arcing. Over time a deposit of carbonaceous material tends to build up on the contacts, distorting the contact surface, insulating the contacts and resulting in overheating of the contact and loss of temper of the contact spring.
Also over time the silver overlay on load top changer contacts may become worn away leaving the copper contact exposed. Exposure of the copper surface to conventional transformer oils tends to catalyze oil oxidation.
One object of the invention is to provide improved transformer load tap changer oils which reduce the build up of deposits on the tap changer contacts and thus extend their in-service life.
Another object of this invention is to provide an oil with improved oxidation stability to minimize the formation of oxidized products in the transformer oil.
A further object of the invention is to provide a load tap changer oil that will provide a film covering any exposed copper surface resulting from wear of contact silver overlay.
Yet another object is to provide an oil that will extend the in-service life of electrical devices such as circuit breakers, switchgear and load tap changers.
These and other objects of the invention will become apparent upon a reading of the description which follows.